Communication devices such as wireless devices are also known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and mobile stations. Wireless devices are enabled to communicate wirelessly in a cellular communication network, wireless communication network or wireless communications system, sometimes also referred to as a cellular radio system or a cellular network. The communication may be performed, e.g., between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN), and possibly one or more core networks, comprised within the cellular communication network.
Wireless devices may further be referred to as mobile telephones, cellular telephones, laptops, or tablet computer with wireless capability, just to mention some further examples. The wireless devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communication network covers a geographical area which is divided into cell areas, each cell area being served by an access node such as a base station (BS), e.g., a Radio Base Station (RBS), which sometimes may be referred to as e.g. “evolved Node B”, “eNB”, “eNodeB”, “NodeB”, “B node”, “node B” or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as, e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Special Mobile). In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs, eNBs or even NBs, may be directly connected to other base stations and may be directly connected to one or more core networks.
The 3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE are controlled by the base stations.
UMTS is a third generation mobile communication system, which may be referred to as 3G, and which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for wireless devices. High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), defined by 3GPP, that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA. Moreover, the 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example into evolved UTRAN (E-UTRAN) used in LTE.
In the context of this disclosure, the expression Downlink (DL) may be used for the transmission path, or send direction, from a base station to a mobile station. The expression Uplink (UL) may be used for the transmission path, or send direction, in the opposite direction, i.e. from a mobile station to a base station.
Packet data traffic is growing very quickly in mobile operator networks, in many cases it grows much more quickly than the rate at which the operator is able to expand network capacity. This leads to more frequent occurrences of congestion in the network, e.g. when the offered traffic is higher than what the RAN is able to fulfill. Also, new services appear often, which may lead to a situation when a new Quality of Experience (QoE) requirement has to be introduced into the network quickly. In this situation, operators need efficient and flexible tools by which they can control how the bottleneck RAN capacity can be best shared so that they can maximize the QoE of their users.
A new type of solution has been put forward in context of a 3GPP User Plane CONgestion management (UPCON) work item, which solution utilizes congestion feedback from the CN to the RAN. This has been documented in 3GPP TR 23.705 version 0.10.0. When RAN indicates congestion to the CN, actions may be taken to mitigate the congestion, such as limiting some classes of traffic, or request to delay some other classes of traffic.
In practice, a wireless communication network, e.g. based on LTE or UMTS, typically comprises an Operation, Administration and Maintenance (OAM) system which may be part of an Operational Support System (OSS). The OAM system comprises functionality and interfaces for an operator of the wireless communication network to operate, administrate, maintain and manage the wireless communication system. A part of the OAM system, which may be referred to as RAN OAM system or simply RAN OAM, is associated with the RAN and responsible for operation, administration, maintenance and/or management of RAN nodes, i.e. nodes comprised in the RAN, or, in other words, radio network nodes. The RAN OAM system typically contains a lot of information based on which an operator may derive when a state of congestion takes place. Such information, which may be referred to as congestion information, may include for example data about the amount of packet loss, packet delay, traffic throughput, air interface utilization, number of connected users, number of connected users with non-empty buffers, etc. A mobile network operator may configure thresholds on one, or on a combination, of these metrics to determine when a state of congestion is considered in its network. It is also possible for a mobile operator to define multiple levels of congestion using the combination of these metrics, so that the congestion mitigation actions can correspond to the current level of congestion.
Current RAN OAM systems work on a per cell or lower granularity. That means that the determination of congestion could be performed on a per cell basis, or for a group of cells, such as cells belonging to the same eNB for LTE, i.e. 4G, or cells belonging to the same Service Area for UMTS, i.e. 3G. In order for the core network to take appropriate mitigation action, the core network also has to find out which UEs are located in a given cell. Hence, the list of affected UEs needs to be determined for the cells which are considered congested based on OAM data.
A solution named 1.5.5 (also called off-path solution) in section 6.1.5.5 of 3GPP TR 23.705 version 0.10.0, suggests a new interface Nq for this purpose. The Nq interface is defined between a new network entity RAN Congestion Awareness Function (RCAF) and the Mobility Management Entity (MME). The RCAF is the node which is assumed to receive RAN congestion related data from the RAN OAM system on a per cell (or lower) spatial granularity. Then, using the Nq interface, the RCAF queries the MME to supply the list of UEs per cell.
A similar approach is suggested for the 3G case, using a Nq′ interface from the RCAF to the Serving GPRS Support Node (SGSN). However, there is a suggested difference. For 3G, the RAN may already have the UE identities as the International Mobile Subscriber Identity (IMSI) may be sent to the RNC. It is suggested that the RAN OAM collects these IMSIs and the RAN OAM then supplies the list of UEs, identified by IMSIs, that were affected by congestion to the RCAF. Hence, for 3G it is suggested that the list of UEs affected by congestion are known to the RCAF without contacting the SGSN over the Nq′ interface.
Besides the UE identities, it is also helpful to receive the list of Access Point Names (APNs) in the RCAF node. An APN identifies an external network where a UE is connected to. Most commonly this is the Internet, but may e.g. be a corporate intranet, or an operator may have its own network for e.g., IMS or MMS, etc. For example may the Gateway GPRS support node (GGSN) or Packet Data Network Gateway (PGW) be selected based on the APN. In other words, the APN is typically needed to know to which packet data network a congestion mitigation action should apply to. The APN may also be used, or even be needed, to determine a proper Policy and Charging Rules Function (PCRF) which may make congestion mitigation decisions. In LTE, the APN may be determined from the MME using the Nq interface. In 3G the APN may be determined from the SGSN using the Nq′ interface.
An alternative solution is named 1.5.4 (also called integrated solution) and is also proposed in 3GPP TR 23.705 version 0.10.0, more particularly in section 6.1.5.4, wherein the RCAF (or RPPF, another terminology applied to the corresponding node) signals the per cell congestion information to the PCRF. The PCRF receives the list of UEs in the given cell using the cell-id sent in uplink user plane data packets from the RAN node up to the PGW, which then forwards the cell-id information to the PCRF so that the list of UEs per cell may be determined.